As the demand for higher data rate services grows, the data rates transferred on wireless channels are increasing. In Universal Mobile Terrestrial Systems communication systems, high data rate high speed downlink packet access (HSDPA) and enhanced uplink channels are being developed. Similarly, CDMA2000 EVDV and EV-DO also use high data rate channels.
As the data rates supported by channels increases, the desire for higher performance receivers also increases. To transmit high amounts of data through these channels, more aggressive modulation and coding schemes are utilized, providing less data redundancy. To achieve desired bit error rates (BER)/block error rates (BLER) at these higher data rates, better receiver performance is desired.
To further improve capacity of wireless systems, antenna arrays are growing in prevalence. These arrays are used to better isolated users and enhance data throughput. Transmission arrays can be used to shape antenna patterns and reception arrays can be used to enhance reception. Although these techniques potentially lead to better capacity and throughput, they create problems at the receiver. Instead of processing information sent from a single transmit antenna to a single receive antenna, processing correlated/uncorrelated information from multiple transmit/receive antennas is required. Also, when a user moves between cells or sectors of a cell, the user is handed off between the cells or sectors. One type of handover is soft (for cells)/softer (for sectors). In soft/softer handover, the user receives and/or transmits from/to at least two cells/sectors. As a result, a receiver during soft/softer handover processes signals from multiple transmission/reception sources.
Accordingly, it is desirable to have high performance receivers.